The present invention relates to a liquid-ring vacuum pump preceded by a precompressor (or supercharger) and followed by a liquid separator, a heat exchanger being provided for transferring heat to a coolant, e.g., water, from a working fluid which has a higher boiling point than that of water.
In a vacuum generating system such as that described, for instance in Siemens Brochure E 7251046, the vacuum pump draws in gas and pushes it together with part of the working liquid, e.g., oil, into the liquid separator, which is disposed on the pressure side of the pump. The compressed gas leaves the separator via an output stub at the top thereof, while the working liquid flows back into the vacuum pump. The heat which is absorbed by the working liquid owing to compression and friction is transferred to the cooling water by means of a heat exchanger located in the working-liquid loop. The cooling water, initially having a temperature of 15.degree. C., for example, is warmed up to the normal working-liquid temperature of 25.degree. to 30.degree. C. and in general is of no further use unless the temperature is brought to a higher level by an expensive heat pump. The friction and compression heat energy which comes in thelast analysis from the operating motor of the vacuum pum is, therefore, lost as a rule.
An object of the present invention is to provide a vacuum generating system in which at least part of this heat is used.